1. Field of the Invention
The present invention relates to a pressure-sensitive adhesive tape or sheet for the medical treatment (i.e., medical pressure-sensitive adhesive tape or sheet; sometimes referred to as xe2x80x9cadhesive tape or sheet for medical treatmentxe2x80x9d or xe2x80x9cmedical adhesive tape or sheetxe2x80x9d in the present specification), and a first aid adhesive tape. More specifically, it relates to an adhesive tape or sheet for the medical treatment, and a first aid adhesive tape to be applied in the field of an attaching material for the medical use, in particular, for a roller bandage, a surgical tape, an adhesive plaster, a poultice medicine, a dressing material, an injury protecting agent, a percutaneous absorbing agent, or the like, particularly suitable for the use of those susceptible for stimulus in the skin, such as the elderly people, infants, and sickly people.
2. Description of the Related Art
As a film for the supporting base material to be used for various kinds of adhesive tapes or sheets for the medical treatment, such as a first aid adhesive tape and a surgical tape, a large number of films containing a plasticized polyvinyl chloride as the main component, produced by a calendar method or the sol cast method have been used conventionally.
The films for the supporting base material containing a plasticized polyvinyl chloride as the main component have such a characteristic that a high stress is provided in the initial stage of applying a tension, but the stress relaxation occurs suddenly according to passage of time. The stress relaxation is derives from the plasticity of the vinyl chloride film. In the case an adhesive tape (or sheet) using the film for the supporting base material having such a characteristic is attached on the skin, the tensile stress is alleviated gradually after the attachment, and consequently the burden on the skin is reduced. By using the film for the supporting base material containing the plasticized polyvinyl chloride as the main component, the attaching operativity can be ensured owing to the appropriate stress at the time of attachment as well as the feeling of being pulled can be eliminated by the stress relaxation thereafter so that the physical skin stimulus can be alleviated. Accordingly, both operativity and low stimulus can be ensured.
However, in the case the plasticized polyvinyl chloride is used, since a large amount of a plasticizer is contained, the plasticizer moves from the film to an adhesive layer, and as a result, deterioration of the pressure-sensitive adhesion force and deterioration of the aggregation force are brought about. Therefore, it is disadvantageous in that the pressure-sensitive adhesive is denatured, the vicinity of the attachment part is fouled due to flow of the pressure-sensitive adhesive, or the like.
Moreover, since the film contains a chlorine, a countermeasure for the post treatment thereof is required for recently in view of the environmental issue.
Therefore, development of flexible thermoplastic resins with a stretchability as a substitute material for the vinyl chloride has actively been promoted not only for the application in the medical field. Various thermoplastic resins such as olefin based resins, ethylene vinyl acetate copolymer based resins, and elastomer based resins have been provided as commercial products.
Specifically, for example, an ethylene methacrylate (EMA) based resin, an amorphous polyalpha olefin based resin, an ethylene vinyl acetate copolymer (EVA) based resin, anolefin based EMA blended product, a polyurethane based resin, a low density polyethylene (LDPE), a linear low density polyethylene (LLDPE) based resin, an ethylene-methylmethacrylate copolymer (EMMA) based resin, or the like, can be presented. In particular, a thermoplastic elastomer resin as an elastic non-chlorine based material has been discussed actively as a prospective material for achieving the above-mentioned object.
As the thermoplastic elastomer resin, for example, first a styrene based thermoplastic elastomer such as a styrene-butadiene-styrene block polymer has been developed. Thereafter, a vinyl chloride based elastomer (TPBC), an olefin based thermoplastic elastomer, an ester based chlorinated plastic based thermoplastic elastomer, or the like have been developed. In particular, the olefin based thermoplastic elastomer is closest to the polyvinyl chloride in terms of the weather resistance, and the cost.
Moreover, the olefin based thermoplastic elastomer improved so as to be hardly flawed has been developed recently. Examples thereof include a polypropylene based alloy with a novel highly blended type hydrogenated styrene butadiene rubber blended.
However, among these various kinds of resins, which can be presented as a substitute for the vinyl chloride resin, only a part of the thermoplastic elastomers are used for a limited area in the medical application, such as an infusion bag, a waste liquid bag for the artificial dialysis, and an infusion tube.
In contrast, application of a soft olefin such as the amorphous polyalpha olefin based resin to the film for the supporting base material is attempted as a substitute film for a polyvinyl chloride resin. However, it is not optimum in terms of the following points.
That is, since it has a low stress with respect to the tension or stretch of any strength, a problem is involved in that the operativity at the time of attachment is extremely poor at the site of medical treatment, or in contrast, a tension is always applied on the skin during the attachment operation due to too high a stress at the time of deformation so that a strong physical stimulus is applied.
Accordingly, the contradicting natures of the operativity at the time of attachment and the skin stimulus cannot be satisfied sufficiently merely by using a conventional dechlorinated vinyl based resin as it is as the film for a supporting base material of an adhesive tape (sheet) for the medical treatment.
From this viewpoint, a large number of those produced by improving a thermoplastic elastomer, which has conventionally been a material for the industrial application, have been proposed as a film for the supporting base material of an adhesive tape for the medical treatment having the same stress relaxation property as that of the vinyl chloride based resin as follows.
The conventional olefin based thermoplastic elastomers are mainly blend based thermoplastic elastomers including a polypropylene (PP) as the hard segment and an ethylene propylene rubber (EPR) as the soft segment. According to the PP/EPR as a common simple blended product, it is poorer than the chlorine based thermoplastic elastomer in terms of the compression set. Therefore, a dynamic cross-linked olefin based thermoplastic elastomer with the compression set improved by slightly dispersing the EPR in the PP while being cross-linked at the time of blending the PP/EPR has been discussed as a substitute resin for the polyvinyl chloride resin.
As the olefin based thermoplastic elastomers to be produced directly in the polymerization stage, for example, an FPO (flexible polyolefins) by Rexene Corp., a catalloy resin by Montell Polyolefins Corp., and a P.E.R. resin by Tokuyama Soda Corp. can be presented.
The catalloy resin is a resin produced by alloying an olefin based resin with an ethylene propylene rubber in the polymerization stage. Compared with the other soft resins (such as a PVC and a PE based resin), it has the excellent characteristics in terms of the heat resistance, and the tearing and piercing strengths. This can be obtained by a polymerization process technique, which has enabled alloying of polyolefins in a polymerization reactor. That is, in gas phase polymerization reactors of a large number of stages, wherein a polymerizing operation is executed each independently such that a polymer obtained in each reactor is taken out as a final product in an alloyed stage. According to this method, a synthetic rubber (ethylene propylene rubber) is blended in a polymerization stage so as to obtain a product with a far higher rubber content compared with a blended product by an extruder, or the like. In such a resin, a phase structure with an EPR phase forming a three-dimensionally continuous matrix, and a PP crystal lamella dispersed therein is provided. As a result, a high elasticity of the polyolefin and a flexibility of the rubber can be related closely, and thus a high initial elastic force and a quick stress relaxation property can be provided.
Moreover, as amorphous or low crystalline olefin based resins, an APAO resin and a CAP resin produced by Ube Industries, Ltd. can be presented. These resins are superior to the conventional olefin based resins in terms of the flexibility and the heat resistance, and furthermore, have a relatively good stress relaxation property.
However, even in the case of using the catalloy resins or the amorphous polyalpha olefin based resins, the stress relaxation property is insufficient, that is, the relaxation tendency becomes extremely dull after a certain degree of relaxation so that softening by the stress relaxation is limited. In particular, even if a small load on the skin, if it remains continuously, depending on the user, it can be recognized as an explicit skin stimulus.
Furthermore, due to poor feeling thereof, in the case they are used for an adhesive tape for the medical treatment of a first aid adhesive tape, the external appearance is poor.
In view of the problems of the technique of the related art, the present invention has been achieved, and an object thereof is to provide an adhesive tape (or a sheet) for the medical treatment and a first aid adhesive tape suitable for attaching on a bending part by using a supporting base material having appropriate flexibility and stress relaxation property as well as a good feeling as a substitute for a polyvinyl chloride film for a supporting base material.
In order to solve the problems, as a result of an elaborate discussion, the present inventors have found out that the problems can be solved by obtaining a base material with a thermoplastic elastomer such as an olefin based thermoplastic elastomer as the base polymer or a part of the base polymer, and containing an appropriate amount of various kinds of additives, which are considered to improve the flowability of a resin so as to complete the invention.